The present invention relates to a piezoelectric resonator arrangement, and particularly to an arrangement constructed as a one-piece unit.
Such resonator arrangements generally consist of a plate-shaped vibrating crystal or piezoceramic to the input and output sides of which are applied coatings for the input and output transducers as well as coatings disposed therebetween on both sides to define the given resonators.
In constructing such resonator arrangements it is particularly desirable to be able to electrically decouple the output and input transducers from one another. The conventional input capacitances of the transducers of such resonator arrangements, or filters, are of the order of magnitude of a few pF and particular care must therefore be taken that the coupling capacitance between the coatings of the input and output transducers remain below about 1 mpF because otherwise sufficient stop band attenuation can not be expected. For example, to achieve a selectivity of an overcoupling capacitance lower than 0.2 to 0.3 mpF would have to be maintained.